Vehicle emissions standards have become increasingly stringent due to the increased knowledge of the negative environmental effects of hydrocarbon emissions, which are generated by fuel vapors into the atmosphere. For vehicles and other fuel-operated devices, controlling and containing fuel vapors is of great importance in reducing emissions. Most vehicles contain an on-board diagnostics system that monitors whether the fuel system is completely vapor-tight. Although it is relatively easy to contain vapors when they are already in the fuel system, the greatest amount of vapor tends to be generated by the refueling process rather than vehicle operation. Past studies have shown that more hydrocarbon emissions were generated during the refueling process than when the entire tank of fuel is actually burned.
More particularly, the refueling process requires a user to remove a closure, such as a gas cap, which seals a filler tube in the fuel system when the gas cap is attached to the filler tube. Although the gas cap is normally designed to be vapor-tight when it is attached to the filler tube, it is common for users to replace the gas cap too loosely, creating a leak. Although some fuel systems have a spring-loaded flapper that shuts the nozzle opening, this flapper simply closes the opening without sealing it. The leak in the fuel system caused by the loose gas cap is detectable by the on-board diagnostics system in the vehicle, which usually indicates the leak by illuminating a “check engine” light. However, because the “check engine” light itself does not specifically indicate that the leak is the problem, diagnosing the leak at the gas cap is time-consuming and inconvenient, particularly in view of how commonly loose caps occur due to user error.
There is a desire for a filler tube closure that can create a vapor-tight seal in a reliable fashion.